Magnaflux

1. How long does it take to get a Quasar system up and running?
The standard startup procedure is one week including in-plant training and development of the Sorting Module. However, startups have ranged from 2 days to many months. The startup duration depends on the level of customer commitment. The two most important issues are:

2. What is the main difference between resonant testing and other NDT Methods?
Other NDT methods identify defective parts by scanning for indications of the defect. The implicit assumption is that the presence and size of the indication correlates with the in-service performance of the part. This assumption is generally not true. Some indications are only superficial and some defective parts show no indications. As a consequence, conventional NDT results in defective parts being shipped while acceptable parts are scrapped. Resonance-based NDT tests parts by measuring their resonant frequencies, which are determined by their stiffness and dimensions-two fundamental parameters that do correlate to performance. Because of this, resonance testing is the ideal technology for effective NDT. Historically however, resonance testing was hampered by the basic limitation that acceptable process variations also affect the resonant frequencies, to the extent that all except the grossest defects are masked. Quasar invented Process Compensated Resonant Testing (PCRT) to provide effective resonance testing in the presence of typical manufacturing process variations. Using PCRT, defective parts can be reliably rejected in a production line environment. PCRT results correlate directly to subsequent part performance.

 

3. How can the customer be certain that an entire complex part has been resonated and tested?
By its nature, resonance is inherently a "whole body" testing method. When the part is vibrated, the energy is distributed throughout the part. However, each feature has its own unique set of resonances, so it is important to assure that the Training Set contains samples of parts with defects located in each area of interest. If this is done, Quasar's software will automatically select a set of resonances which collectively represent each location.

 

If there is a defect in a location that is not represented in the Training Set, then there will be some question as to whether it will be rejected. If the defect is relatively large, it will be rejected, but if the defect is small it will probably be accepted.

4. How are parts selected for the Training Set?
The Training Set is the fundamental basis for developing the Quasar Sorting Module. It must contain good parts that represent the acceptable range of process variation. For example, consider a permanent mold casting process that uses 20 cavities. Several parts (3 to 5) should be included from each cavity. Typically, the cavities are rebuilt periodically. So the parts should be sampled over the rebuild period. In this case, the good part sample would be 60 to 100 parts.

 

The bad parts should also represent the process variation, but it is more important that the bad parts represent the range of defects and defect locations of interest.

 

It is extremely important that each part be evaluated to assure that it is properly classified. The basis for this classification is other NDT methods and engineering judgment. Since these methods are known to be fallible, destructive evaluation is required for parts where the Quasar test result disagrees with the other methods.

5. For what size production run does it make sense to use Quasar testing?
It typically requires from a few days to two weeks to develop and check out the Quasar Sorting Module for a given part type, so the production run has to be large enough to justify this effort. Typically, Quasar is used for parts made in quantities of at least 100,000 parts per year, although if the part is quite valuable or is safety-critical, it may be justified for runs as small as 10,000. The maximum run rate in current operation is about 3600 parts per hour, using two Dual Test Station systems with automatic loading.

 

6. How many parts are necessary to calibrate a Quasar unit?
Normally, the Training Set of parts starts with about 100 Good parts and at least 50 Bad parts. Other parts may be added later to reflect changes in the process over time.

 

7. How does the vibration energy excite the part and how is the part response then measured?
Quasar transducers transmit energy into the part and sense the part's response to that energy. The transducers, designed by Quasar, are based on piezoelectric ceramics (PZT) and are similar to the transducers used for ultrasound NDT.

 

During the test, the part is in contact with 3 transducers, one "drive," and two "receive." The Quasar Transceiver generates a continuous wave (CW) signal for the drive transducer and simultaneously measures the output of the receive transducers. (It is important that nothing else touches the part while it is being tested.)

8. How many parts can be tested on one Test Station?
Any number of parts may be tested on a standard single or dual Test Station by means of drop-in Test Heads designed for a single part or a dimensionally similar family of parts. Multiple small parts can also be tested on a single drop-in Test Head, but the number is limited by part geometry, the cost of the additional complexity of the mechanical design and control system, and possible loss in part measurement precision associated with multi-use tooling.

9. How much plant noise can the Quasar system handle?
The Quasar system is designed to be co-located with other production equipment. It will operate successfully in a typical heavy manufacturing environment in terms of floor or air-transmitted noise. In unusual circumstances close proximity to high-energy percussive or vibration sources may require some additional isolation for the Quasar system.

 

10. What is a typical test cycle time?
The typical test cycle time ranges from 1 second for very small parts such as ceramic balls to 20 seconds for large parts such as engine blocks. The load/unload cycle requires additional time. Individual systems in current production range from 120 to 1800 parts per hour.

11. How is the Quasar system calibrated?
Quasar's fundamental measurement is frequency, which is generated and sensed by the Transceiver. The Transceiver is calibrated to international standards when built. In addition, there are two types of calibration used for production systems. Quasar recommends that the Hardware Verification Test (HVT) be run at the beginning of each shift. The HVT verifies that all equipment is performing within tolerance. While infrequently required, Quasar also has a procedure for re-calibration of the Transceiver. This is a relatively simple test using a frequency counter that can be performed by any electronics calibration facility.

12. What is Quasar's statistical process capability?
The Quasar system records test results, passes and fails, and test parameters for each part in a local database. The system displays first pass and second pass failure rates and throughput statistics. The recorded data file is available for input to any statistical program.